Missile proportional navigation system using fixed seeker

ABSTRACT

The outputs of a fixed array detector are employed as inputs to a homing missile steering system using proportional navigation. The seeker outputs are in the form of quantized signals, and are summed with gyro-derived attitude signals to produce missile control signals.

United States Patent 1151 3,706,429 Welford et al. 1 Dec. 19, 1972 541 MISSILE PROPORTIONAL 3,223,357 12/1965 Broecker-Steinkuhl ..244/3.19 NAVIGATION SYSTEM' USING FIXED 3,165,749 1/1965 Cushner ..244/3.19 X SEEKER Primary ExaminerBenjamin A. Borchelt [72] Inventors: Gordon D. Welford; Buster E. Kel- Assistant Examiner-Thomas H. Webb ley, both of Huntsville, Ala. Attorney-Harry M. Saragovitz, Herbert Ber] and [73] Assignee: The United States of America as Aubrey Dunn represented by the Secretary of the [57] ABSTRACT Navy The outputs of a fixed array detector are employed as [22] Filed: 1,970 inputs to a homing missile steering system using pro- [21] APPL 7 3 portional navigation. The seeker outputs are in the form of quantized signals, and are summed with gyro- 7 derived attitude signals to produce missile control [52] US. Cl "244/119 signals. [51] Int. Cl. ..F41g 7/00, F42b 15/02, F42b 15/10 [58] Field of Search ..244/3.19

[56] References Cited 3 Claims, 1 Drawing Figure UNITED STATES PATENTS D V I i 3,189,300 6/1965 Robert .2541119 A9,, SAMHLE AND 1 1101.0 I 70 1 PULSER 108 I04 |oo SAMPLE ATTITUDE J AND POSITION vAX DELAY HOLD GYRO SAMPLE FIXED AND SEEKER HOLD ARRAY MISSILE PROPORTIONAL NAVIGATION SYSTEM USING FIXED SEEKER BACKGROUND OF THE INVENTION This invention is in the field of guided missiles which employ proportional navigation systems. Proportional navigation is a guidance technique currently used in missiles homing on moving targets. The homing may be passive, active, or semi-active. The technique requires measurement of the rate-of-change of line-of-sight(s) between the missile and a target. This measurement is usually accomplished with a gimbaled seeker on the missile. The seeker continuously tracks the target by torques applied to its gimbals, with the average torques providing line-of-sight rates. Navigation angles are computed from the line-of-sight rates. Alternatively, the line-of-sight rate is determined by differentiating a signal from a gimbal angle pickoff and subtracting this signal from a gyro-derived missile attitude rate signal. A gimbaled seeker for this purpose requires a twodegree-of-freedom gimbal, two' independent servo loops (including torquers), and a two-degree-offreedom position or rate gyro. Fixed seekers are well known and have some desirable features, but are not employed in proportional navigation. Their use has been limited to simple pursuit problems, primarily because of the problem of accurately determining the line-of-sight rate signal.

The instant invention is able to combine the desirable features of a fixed seeker and a proportional navigation system.

SUMMARY OF THE INVENTION A homing missile with a proportional navigation system employs a fixed array seeker for determining line-of-sight of a target. The seeker has quantized output signals, which signals are summed with gyroderived attitude signals. The sum signals are subsequently sampled and combined with themselves to provide control signals.

BRIEF DESCRIPTION OF THE DRAWING The single drawing FIGURE shows a schematic diagram of the invention, for one servo system.

DESCRIPTION OF THE PREFERRED EMBODIMENT In this description, it is assumed that a target on which the missile is homing presents a continuous image to fixed seeker array 60 of the drawing. That is, the target is not being illuminated with pulsed energy, (for active of semi-active homing), nor is it emitting pulsed energy (for passive homing). Array 60 may consist of a matrix of photodetectors (for visible and IR radiation) or horns (for UHF, etc.) but its particular makeup is unimportant to the invention. It is assumed that the target image is of such size that only one element of the array is illuminated at any one time, and that the array has a descrete output for each element. This may be accomplished by having the array in a matrix of rows and columns, with the rows connected in one ladder network to give an output for vertical angles, and with the columns connected in another ladder network to give an output for horizontal angles. For the sake of simplicity, only one output will be considered in describing the invention. Obviously, the other output may be used to control another servo loop in similar manner to the one herein described. The output of 60 is designated b on the drawing, and is applied to sampleand-hold circuit 98. The output of 98 is designated 45* and is applied to an input of summing network 104. Also applied to 104 is an attitude signal 0 from attitude position gyro 100. The output of 104 is applied to sample-and-hold circuit 106. The output A from 106 is the output at the ith sampling instant. It should be understood that sample-and-hold circuits 98, 106, and 120 (yet to be described) all are operated by pulser 70, which pulser generates short pulses which cause each of these circuits to periodically sample their inputs, and hold the level thereof until the next sample period. Output A is delayed by one sample pulse period in delay cir cuit 110 and is applied to an input of summing network 112. The output it is also applied directly to another input of 112. The output from 112 is the difference between its inputs and is proportional to the rate-ofchange of I, or AA. The AA signal is multiplied by the constant gain factor N in block 114 to give the update angle, AO which is applied to an input of summing network 118. The output of 118 is applied to sampleand-hold circuit 120. The output command angle, 0 ,.at the output of sample-and-hold circuit 120, is fed back to another input of summing network 118 by lead 122 and to an input of summing network 124 by lead 123. The signal 6,, on leads 122 and 123 is the missile attitude command and has subtracted therefrom the true attitude 0 in summing network 124 to give error signal e, on lead 128. Signal 6 is applied to controller 24. This controller controls the attitude of airframe 26, for guiding the missile toward an intercept point with the target. The attitude of the air frame is sensed by attitude position gyro 100, to obtain 0.

In the above discussion, it has been assumed that a continuous target radiation was present. If the target is illuminated by a source such as a pulsed laser, it would be necessary to have pulser synchronized with the laser. This could readily be accomplished by a radio transmitter-receiver link between the laser pulser and pulse 70, or by using the pulsed output of the detector array as a trigger for pulser 70.

We claim:

1. A missile guidance system for proportional homing navigation on a target, comprising: a fixed seeker array having an output, for providing a quantized output signal in accordance with the position of a target image on said array; means connected to said output for deriving a control signal related to rate-of-change of said output signal, and missile control means connected to said means for deriving; wherein said means for deriving includes a first summer having inputs and an output; a first sample-and-hold circuit connected between said output of said array and said input of said summer; a second sample-and-hold circuit having an output, and an input connected to the output of said first summer; a one sample time delay circuit having an output, and an input connected to the output of said second sample-and-hold circuit; a second summer having an output, and having inputs respectively connected to the output of said delay circuit and said output of said second sample-and-hold circuit; a third summer having an output and inputs; an amplifier conl060ll 0687 nected between said output of said second summer and an input of said third summer; a third sample-and-hold circuit having an input connected to the output of said third summer and having an output; a fourth summer having an output, and inputs, with one of said inputs connected to said output of said third sample-and-hold circuit; said output of said third sample-and-hold circuit being connected to another input of said third summer; and said missile control means including an airframe controller having an input connected to the output of said fourth summer; said means for deriving l060ll 0688 UNITED sTArEs PATENT OFFICE CERTIFICATE OF CORRECTION 3,706,429 Dated December 19, 1972 Patent No.

GordondD. Welford et a1. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

v On the cover sheet [73] "The United states ofAn lerica as represented by the Secretary of the Navy" should read The United States ofAmerica as represented by the Secretary'of the Army Signed and sealed-this 26th'day of February 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

Attesting Offi C. MARSHALL DANN Commissioner of Patents USCOMM-DC 60876-F'O9 FORM PO-IOSO (10-69) u.s. sovsmmsm manna omcz: as; o-su-su, 

1. A missile guidance system for proportional homing navigation on a target, comprising: a fixed seeker array having an output, for providing a quantized output signal in accordance with the position of a target image on said array; means connected to said output for deriving a control signal related to rate-of-change of said output signal, and missile control means connected to said means for deriving; wherein said means for deriving includes a first summer having inputs and an output; a first sample-and-hold circuit connected between said output of said array and said input of said summer; a second sample-and-hold circuit having an output, and an input connected to the output of said first summer; a one sample time delay circuit having an output, and an input connected to the output of said second sample-and-hold circuit; a second summer having an output, and having inputs respectively connected to the output of said delay circuit and said output of said second sample-and-hold circuit; a third summer having an output and inputs; an amplifier connected between said output of said second summer and an input of said third summer; a third sample-and-hold circuit having an input connected to the output of said third summer and having an output; a fourth summer having an output, and inputs, with one of said inputs connected to said output of said third sample-andhold circuit; said output of said third sample-and-hold circuit being connected to another input of said third summer; and said missile control means including an airframe controller having an input connected to the output of said fourth summer; said means for deriving further iNcluding means for determining missile attitude having an output connected to an input of each of said first and fourth summers.
 2. The system as defined in claim 1 wherein said amplifier has an amplification factor equal to the navigation factor of the missile.
 3. The system as defined in claim 2 wherein said second and fourth summers include means to determine the difference between signals applied to the inputs thereof. 